1. Field of the Invention
The present invention relates generally to medical treatment apparatus and more specifically to a method and apparatus that provides muscle-assisted pumping of venous blood from legs. The purpose of this apparatus and method is to prevent a medical condition called deep venous thrombosis (DVT) and also to reduce and/or to prevent leg and ankle swelling in persons who are motionless while standing or sitting for extended periods of time. This concerns, for example, travelers on long haul flights or in cars, computer operators, salespersons, etc.
The method and the device as described in the present invention utilize electrically stimulated calf muscles in legs. The stimulation causes rhythmical contractions of muscles in both calves, which in turn squeeze out venous blood from intramuscular veins and deep central veins in legs. This results in forced venous blood flow from legs upwards against gravity in the direction of lungs and heart. This is augmented by the action of valves inside the veins which prevent the return of squeezed blood volume back into leg veins.
To obtain such rhythmical and effective muscle contractions, a special kind of electrical neuromuscular stimulation device is used. Such device and method of its application for the above purpose is the subject of this instant invention.
The present invention of stimulation method and device thereof utilizes a continuous train of very short electrical impulses at a predetermined durational range and frequency wherein, superimposed on top of this continuous train of electrical impulses, there are rhythmic (cyclic) periods of modulated bursts of energy associated therewith. The timing of these bursts of energy approximates or is close to a heart rate and the electrical stimulation is delivered by means of two electrodes while only one stimulating electrode is applied to a skin of each leg.
2. Description of the Prior Art
Numerous Electro-stimulation Devices have been provided in prior art. For example, U.S. Pat. Nos. 1,908,688, Re. 32091, 6,701,189, 2,375,575, 4,712,558, 3,083,712, 5,048,522, 3,516,413, 5,350,415, U.S. Patent application No. 2002/188331, U.K. Patent No. GB2085733, PCT Patent Application WO 95/33516 to Pick et al., all are illustrative of such prior art.
There are three known muscle stimulation devices and methods; they are low frequency stimulators, high frequency interferential stimulators and Russian-Current stimulators. These three basic types have their respective advantages and disadvantages, but none of them can provide stimulation with optimal effectiveness and safety combined with the ease of use. In addition the pain usually compromises their effectiveness, when electricity is applied over the skin. Furthermore, they are neither easy nor practical to use, as they usually require applying at least two and up to six electrodes and associated connecting cables for each stimulated muscle.
The most common of commercially available muscle stimulators are so-called “LOW FREQUENCY” electrical stimulators. They are used both in medical field and non-medical applications. Many are battery powered and some of them are suitable for individual use at home. Their utilization is broad, ranging from rehabilitation, sport medicine, aid to athletic training, body building and shaping, to slimming, anti-cellulite and beauty applications. They are inexpensive, not always easy to use and are marginally effective and uncomfortable. These LOW FREQUENCY stimulators can deliver electrical impulses in various time sequences. The time sequences, frequencies and other impulse parameters are usually controlled by the health professional or by the users themselves. These impulses are delivered to motor points on the user's skin via electrically conductive pads. This results in muscle contractions that are either too weak and too superficial to be effective. The user of these LOW FREQUENCY stimulators may also incur a pain during tetanic muscular contractions which further limits the effectiveness of these LOW-FREQUENCY stimulators. For the stimulation to be effective it must produce many maximally strong but painless contractions, at a level preferably close to that of MVC (maximal voluntary contraction) force. The most limiting factor for effectiveness of LOW-FREQUENCY stimulators is an increasing pain associated with the increasing intensity of stimulation. Such pain does not usually permit the achievement of high intensity stimulation levels necessary to produce strong muscle contractions. This is due to the shape, frequency and character (waveforms) of the electrical impulses, produced by these stimulators. The quasi-rectangular mono-phase or bi-phase stimulation current waveform are most commonly used impulse shapes in these LOW FREQUENCY stimulators. The time pauses between these impulses, called inter-pulse intervals, are in the range from 0.01 second to 1 second, which respectively correspond to the frequencies of 100 Hz (Hertz) down to 1 Hz, with a most commonly used frequencies around 50 Hz. The impulse durations (widths) commonly used in these stimulators are in a range from 300 to 800 microseconds. Some stimulators in this category include programmed sequences of impulse durations and frequencies stored in their internal electronic memory. The program and execute modes to accomplish storage of frequency and impulse duration parameters by using electronic memory were disclosed by Morales and Burdette in the U.S. Pat. No. 4,528,984.
Unfortunately, the frequency and impulse duration ranges of LOW FREQUENCY stimulators lie within the same range as the maximal sensitivity of the pain receptors in the human skin, which is around 50 Hertz and therefore cause pain in association with tetanic muscle contractions.
The second type of the above mentioned trans-cutaneous muscle stimulators are “HIGH FREQUENCY INTERFERENTIAL” stimulators. They are suitable mostly for clinical use as they require line power and must be applied by health professionals. They are more effective than most domestic LOW FREQUENCY stimulators and are relatively painless, but possess the disadvantage of being unsafe for use by untrained persons. Furthermore, these HIGH FREQUENCY INTERFERENTIAL stimulators are expensive and bulky. They deliver two stimulation waveforms simultaneously in crossway geometric pattern. The waveforms are continuous and sinusoidal in shape and operate in a frequency range from 2000 Hz to 5000 Hz. These waveforms are mixed in the tissues under the skin by so-called interference, which produces a beat frequency in a range very similar to that of the “LOW FREQUENCY” stimulators (1 to 100 Hz). However, their effectiveness is limited by the fact that the trained operator is unaware of the location that the interference beat frequency is produced beneath the skin, thereby making direct targeting treatment difficult.
The third existing type of neuromuscular stimulators, called “RUSSIAN CURRENT” operates also in the same high frequency range as discussed above with respect to the HIGH FREQUENCY INTERFERENTIAL stimulators. However these RUSSIAN CURRENT stimulators do not function using the interference phenomenon. The RUSSIAN CURRENT stimulators produce a single type of stimulation waveform per channel. The Russian Current waveform is usually sinusoidal in shape and it has high frequency oscillations ranging from 2000 Hz to 5000 Hz. This sinusoidal waveform oscillations are interrupted every 0.01 to 0.02 seconds. These stimulators are painful and unsafe for use by untrained persons and are also expensive and bulky.
While all these stimulators may be suitable for the particular purpose to which they address, they would not be as suitable for the purpose of the present invention as heretofore described.